You want to install Linux on a machine and you don't have any CD or DVD to burn the image file! You can make use UNetbootin.
This small software available for Windows, Linux and Mac allows you to create bootable drive containing a full Linux distribution (installer) or any ISO.
For Linux users, enter the following command:
Once installed select the distribution of your choice as well as the path to your USB! UINetbootin will handle the rest ...
It will recover the required ISO directly from an FTP source
Unpack the ISO on the USB key
Make the USB bootable
The "Space used to preserve files across reboots" option allows you to create a persistent data area on your USB key, e.g keeps all the files that are stored in this area, even after reboot and connection to other computers . The option can be used when running a portable version of Linux from a USB key.